Work is continuing on the Histopathologic Study of Pigmented Ocular Tumors. Continuous cell lines of choroidal melanoma and other intraocular tumors are being established and maintained. The ultrastructural characteristics of the cells and the original tumors are being studied. In addition correlative investigations of the DNA polymerases of these ocular tumors and corresponding normal tissues are under way. Studies to date indicated the presence of RNA-directed DNA polymerase (reverse transcriptase) in retinoblastoma cells and in some choroidal melanomas. This activity is increased when cells are treated with BUDR. Treatment of patients with P32 or radioactive iodinated chloroquine results in absence of reverse transcriptase activity. In addition to studies of human ocular tumors experimental models have been studied including Greene melanoma tumors resulting from placement of cells into the choroid; ocular tumors induced in cats with Rickard sarcoma virus and ocular tumors in chickens induced with avian herpes virus.